Tiangong Ultra

What it is

Tiangong Ultra is the humanoid robot entered in the 2025 Beijing Yizhuang humanoid half marathon by the Beijing Humanoid Robot Innovation Center^[1][2]. It stands 180 cm tall; CCTV reported its weight as 52 kg, and the China Securities Journal gave about 55 kg^[1][2]. Height and mass are not trivia for a machine that moves on two legs: every kilogram has to be accelerated, braked and balanced by the motors and the control software, and all of it has to be carried around the course on whatever energy the battery holds.

The robot ran on "Huisikaiwu", a platform developed by the same centre, which describes it as providing an embodied brain and cerebellum for long-range perception and planning^[2]. The phrase points at a split between deciding and doing: one part of the system takes in the surroundings and works out a route, another handles the moment-to-moment control of joints and balance.

The race

The course was 21.0975 km long^[1]. Tiangong Ultra won the race on 19 April 2025, crossing the finish at 10:14 after 2 hours 40 minutes 42 seconds, an average speed of 7.88 km/h^[1]. That is roughly the pace of a brisk human jog, held for well over two and a half hours.

Energy is where a half marathon becomes an engineering problem rather than a short demonstration. The robot made its first battery swap at the 5 km mark, and the swap took 1 minute 50 seconds^[1]. A swap is used instead of recharging because filling a pack takes far longer than a race allows; the price is that the clock keeps running while the machine is stopped, so the time a swap costs is part of the result.

The fall

After about two hours of running, the robot fell on a narrow straight^[1]. The reported cause was an inaccurate battery reading, and it got up and continued^[1]. A wrong estimate of remaining charge is not a small matter for a walking machine: the plan for the next few steps — how fast to go, how much torque to ask of each joint — rests on an assumption about how much power is available. Falling, getting up unaided and carrying on is the part of the story that says most about the state of the control software, because recovery has to happen without a human stepping in to reset the machine.

Where it sits

A timed public race turns a laboratory capability into a comparable number. Finish time, average speed, how often the battery has to be changed and what happens when something goes wrong are all measurable, and other teams can be set against them. Long distances also load parts that short demonstrations never reach: joints, thermal limits, the drift of sensors over hours of operation.

Tiangong Ultra was the centre's entry, and the centre is also the developer of the platform it ran on^[1][2]. The result therefore describes one organisation's stack from the planning software down to the running gear — the machine, the battery handling around it, and the perception and planning layer that kept it moving.